The debates have been contentious and have often centered on whether the vapor released can hurt the health of bystanders.

Each brand of e-cig is different. The federal government does not regulate the contents and some vapers home brew their e-liquid on their own. But some of the common ingredients are distilled water, flavoring, vegetable glycerin (sometimes used in personal cosmetics), propylene glycol and nicotine.

“There are small trace amounts of nicotine,” said Jason Cardiff, CEO of the California electronic cigarette company Cigirex. “In the testing that’s been done, it’s not enough that can be picked up second-hand by anyone.”

Cardiff says e-cigarette vapor is harmless. Maybe you’d like to hear that from someone who’s not trying to sell you a product, but for now the federal government is silent. The Food and Drug Administration is considering regulations for electronic cigarettes, but that decision has been delayed for months.

In the meantime, local jurisdictions have stepped in with their own laws and opinions.

“I’m a firm believer that those laws will be unwound, and everybody will come to understand that you can’t treat an electronic cigarette like a regular cigarette,” Cardiff said.

New York City passed its indoor e-cigarette ban in less than three weeks, and policy watchers say there’s similar public-health muscle in Philadelphia. Remember: Philly cleared the air of traditional cigarettes smoke before Pennsylvania passed its indoor air law.

In December, the New York City hearing on electronic cigarettes ban was contentious. At City Hall, while some people stood to give speeches, some ban opponents made their point by ‘puffing’ on electronic cigarettes.

“Some have a coffee flavor, some have a mint flavor” said Karen Blumenfeld, who was at the meeting. “Imagine taking all those smells and putting it in one room.”

Blumenfeld leads GASP: Global Advisors on Smoke Free Policy.

“Many people present, including myself, were getting headaches, many people were getting nauseous,” she said. “Nicotine can create headaches. It’s no surprise that people who are non-users were becoming sick from this.”

Blumenfeld’s group helped push through the country’s very first e-cigarette ban in Paramus, N.J., back in 2009. Since then, there’s emerging science, Blumenfeld said, and even more health worries about the fumes that get released when vapers "light up."

The arguments from the industry have not changed, she said.

“They say: ‘We need more time to evaluate, we need more time, we need more time,’" Blumenfeld said. “We never hear any empathy for the innocent bystander who needs to breathe in the second-hand vapor smoke.”

Traditional tobacco makers — including Reynolds America and Lorillard are now competing in the electronic-device marketplace. Jeff Stier, with the National Center for Public Policy Research, says that affiliation has created some "knee-jerk" opposition to vaping.

“There’s almost an ideological view here, well if Big Tobacco is involved, if it gives people pleasure, if somebody’s making money off of it, it must be bad,” Stier said.

Instead of making electronic cigarettes "public-health enemy No. 1," Stier said the government needs to regulate e-cigs according to their risk.

“E-cigarettes are a fantastic alternative for people who’ve had a hard time using other methods,” Stier said. “E-cigarettes may do more good for public health by getting people to quit smoking than any tax, warning label has ever done.”

Stier points to a long list of research that he says supports that belief. Those particular studies show e-cigs are less harmful than traditional smoking.

Blumenfeld and others believe a completely different stack of studies.

“There’s no proof that e-cigarettes are an effective stop-smoking tool — over the long term,” she said.

Gregory Conley, 26, started smoking regular cigarettes as a teenager, then in his early 20s he tried watermelon-flavored electronic cigarettes.

“Overnight I was no longer a smoker,” Conley said.

Before that he’d tried nicotine gum and lots of other stop-smoking tools.

“I struggled to quit for many years,” he said.

Conley said vaping offered him not just nicotine, but the ability to inhale and mimic his old smoking behaviors.

Conley got a law degree, and these days he’s a professional advocate for the electronic cigarette industry.

Conley is an adviser for Consumer Advocates for Smoke-free Alternatives Research Fund, which funded a review of the chemistry of the vapor and liquid in e-cigarettes.

Conley lives in New Jersey where e-cigs are banned in restaurants, but — for now anyway — when he visits Philadelphia, he’s free to vape. Nonetheless, Conley usually takes a "stealth" approach.

“You learn that as long as you are not releasing giant clouds, no one’s going to notice, and the few people who do notice nobody cares,” he said.

“If you hold your breath for five seconds, and then exhale nothing comes out. Or if you’re drinking a hot beverage and you pull your coffee up to your mouth it looks like steam,” Conley said.

Conley said he "stealth vapes" to be respectful of the people around him — not because he thinks the vapor is harmful.

“Propylene glycol is the same ingredient they use in fog machines,” Conley said. “If you go to the Troc or the TLA, you are going to be exposed to more propylene glycol that one night than you will ever be exposed to sitting in a café with a e-cigarette user.”

Conley is against government bans on indoor e-cig use, but says he has no problem with private businesses that make their own rules.

Celia Joseph an employment attorney with Fisher & Phillips, LLP says there is a patchwork on-the-job rules about vaping. Generally, employers can set their own policies, but many haven’t.

“What they don’t have are actual statements from the FDA saying: ‘It’s safe or not safe,’” Joseph said.

“Proactively I think they should assess for themselves, if somebody is vaping in the workplace, is that safe? That’s something they have to decide for themselves,” she said.

Or maybe there is some other reason they don’t want it there, Joseph says.

“State and local have been stepping and enacting their own law, and for very different reasons,” Joseph said.

Some supporters of e-cig bans say the devices glamorize traditional smoking. Others worry they appeal to teens who’ve yet to develop a nicotine habit. Another group has said the "look-alike" product will lead to confusion for public establishments that are trying to enforce existing bans on combustible cigarettes.

Joseph helps big companies write employee handbooks and her advice is: Don’t wait for that moment when a worker comes in complaining about vaper in the next cubicle over.

"It's so much better to have a policy and think that through before that first time," Joseph said.